docs: add README file for packages

packages/README.md

@@ -0,0 +1,75 @@
+# Packages
+
+## Creating new package
+
+1. Create a new folder inside `packages/<your-package>`.
+2. Add `package.json` file:
+```json
+{
+  "name": "@react-native/<your-package>",
+  "version": "1000.0.0",
+  "description": "Package description",
+  "keywords": [
+    "react-native"
+  ],
+  "homepage": "https://github.com/facebook/react-native/tree/HEAD/packages/<your-package>#readme",
+  "bugs": "https://github.com/facebook/react-native/issues",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/facebook/react-native.git",
+    "directory": "packages/<your-package>"
+  },
+  "license": "MIT",
+}
+```
+2. Add `README.md` and an `index.js` file
+
+### Setting up build step for packages containing `flow` types (Optional)
+
+1. Make sure the package implementation is placed inside of `src` directory (this is what the `build.js` script expects).
+2. Add `.gitignore` file containing: 
+
+```
+# Dependencies
+/node_modules
+
+# Build output
+/dist
+```
+
+3. Add following properties to `package.json`:
+
+```json
+{
+  //...
+  "exports": {
+    ".": "./src/index.js",
+    "./package.json": "./package.json"
+  },
+  "files": [
+    "dist"
+  ],
+  "engines": {
+    "node": ">=18"
+  }
+}
+```
+
+- Next, in `scripts/build/config.js` add `<your-package>` inside of `buildConfig` object, like so:
+```js
+const buildConfig = {
+  packages: {
+    '<your-package>': {
+        target: 'node'
+    }
+  },
+};
+```
+
+- Optionally you can specify `buildOptions` for example: whether to emit TypeScript definition files (`.d.ts`).
+
+In order to verify if new package was configured properly run `yarn build` in the root directory and check if `packages/<your-package>/dist` folder contains newly created files.
+
+
+
+